الفهرس 
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Abstract
Nephrolithiasis is a multifactorial disease caused by environmental, hormonal and genetic factors. Gene polymorphism has been reported to be an important factor which increases the susceptibility of nephrolithiasis. Calcium-containing stones comprise 70% to 85% of all stones.
Vitamin D receptor (VDR) plays a key role in calcium metabolism, and is closely related to urinary stone formation. Previous studies have investigated the associations between VDR single nucleotide polymorphisms (SNPs) at BsmI, ApaI, FokI, or TaqI cutting sites and nephrolithiasis in different populations. However, the results remain inconsistent and controversial.
As the most frequently seen polymorphism within the VDR gene is BsmI, it has been used as a genetic marker in searching for the cause of nephrolithiasis. In this regard, the present study aimed to investigate the association of BsmI gene polymorphism in calcium nephrolithiasis patients.
For this purpose, this study was conducted on thirty (30) calcium nephrolithiasis patients diagnosed by CT stone protocol and fifteen (15) age- and sex- matched controls. Subjects were selected from the Urology Department and Clinics at Ain Shams University Hospitals. Subjects with evidence of hypercalcemia were excluded from the study.
All individuals enrolled in this study were subjected to the following: full history including family history, clinical examination and laboratory investigations (urine analysis, calcium creatinine ratio in random urine sample, serum electrolytes and renal function tests). Imaging study including CT stone protocol was done for patients in addition to chemical stone analysis. For controls, pelviabdominal ultrasound was done to exclude renal stones. Finally, assay of BsmI polymorphism of the VDR gene by Polymerase Chain Reaction -Restriction Fragment Length Polymorphism (PCR-RFLP) was done for all subjects.
The study revealed that no statistically significant association was found between VDR BsmI polymorphisms (BB, Bb, bb genotypes) and the studied calcium nephrolithiasis patients. Comparative analysis of the VDR BsmI genotypes showed higher distribution of BB mutant homozygous genotype in calcium nephrolithiasis patients compared to control group (16.7% vs. 6.7%), however, it did not reach a statistical significance. In addition, although B allele was more frequent in patients’ group than in controls (43.3% vs. 30%), no statistical significance difference was found. On the other hand, the bb genotype (wild type) and b alleles were more frequent in controls compared to calcium nephrolithiasis patients (bb genotype = 46% vs. 30%, respectively; b allele =70% vs. 56.7%, respectively) without reaching a statistical significance. Moreover, no statistically significant association was detected between BsmI genotypes and the studied groups in both recessive model (bb vs. BB and Bb) and the dominant model (BB vs. Bb and bb).
In conclusion, our findings revealed that, there was no significant difference in frequency of the (BB, Bb and bb genotypes) in the calcium nephrolithiasis patients compared to control group. This agrees well and goes in accordance with previous results in various ethnic and geographical distribution studies on the same gene polymorphism BsmI polymorphism.